What's causing "The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store." on startup?

You are quite right - Day One was causing the issue.

I have found that I can fix it without uninstalling Day One.

I disabled 'Show Menu Bar Entry' in the Preferences. Restarted. Re-enabled Menu Bar Entry. Restarted again.

Now I have Day One running and no error message.

Thanks All

My solution was to delete Day One 2.0 as well. Day One says to just update to the current version to fix it. I did that and everything seems to be running smoothly.

To potentially track down the culprit, open Activity Monitor and leave it open. Determine if "Chronicle" or something else appears as an open app or process when that prompt appears.

Refer to Welcome to Activity Monitor on Mac - Apple Support and How to use Activity Monitor on your Mac - Apple Support.

Thank you guys, same here, 'Day One' app was the culprit. Deleted the app from my iMac and the message is gone. I do hope they are aware of this issue. Will send a report to Day One support anyway.

I wonder why the error message doesn't give any clue to what's causing it. Felt a bit lost, like in those old Windows days ... 😉

Do you use the app called Day One? I was getting the same error, and upon opening Activity Monitor (thanks John Galt) I realized that bookmark in the error matched the bookmark belonging to Day One Helper. I also knew that Day One had updated the day before AND noticed that the bookmark icon that is usually present in my menu bar was absent. I opened the app and just did a general settings check, had to recheck for it to sync, and did not see the error message on my next restart. The bookmark is back in the menu bar too. Hope this works for you and continues to work for me! 🙂

Do you use the app called Day One? I was getting the same error, and upon opening Activity Monitor (thanks John Galt) I realized that bookmark in the error matched the bookmark belonging to Day One Helper. I also knew that Day One had updated the day before AND noticed that the bookmark icon that is usually present in my menu bar was absent. I opened the app and just did a general settings check, had to recheck for it to sync, and did not see the error message on my next restart. The bookmark is back in the menu bar too. Hope this works for you and continues to work for me! 🙂

I agree that the problem is associated with Day One Journal. When I looked at the Activity Monitor under process name, Day One Helper comes up with the same pink bookmark icon that shows in the message noted, “The managed object...” Recently I had removed Day One from my dock. This might have triggered the annoying message.

For me, it was Day One Journal. For whatever reason, it was no longer displaying in the toolbar after updating. I suspected it was something at startup and finally narrowed it down to that app.

I am having this same issue...So far it only happens when I do a complete restart of my iMac, so trying to make use of Activity Monitor unfortunately is not an option.

However, I notice that the weird coral colored "bookmark" logo is for the Day One app. Buse, do you have that app installed on your machines?

It appears to be caused by an app named "Chronicle". I am not familiar with a product by that name.

Thank you for your help. Day One Journal was indeed the problem and fixed via preferences as described by FotoChromic.

Have never had this error in the past. I just did the upgrade to the latest version of High Sierra 10.13.4 and this error was the first thing I saw.

Update: Checking the Day One app did the trick. Thank you!!

Do you have Day One Journal. ?

Have never had this error in the past. I just did the upgrade to the latest version of High Sierra 10.13.4 this morning and this error was the first thing I saw.